Means for damping vibratory structures of vibration apparatus



MEANS FOR DMEIPENG VIBRATORY STRUCTURES OF VIBRATION AiPARATUS Mimi 0%.22. 192% TEIIEICH HJECH'I, HUGO LICHTE, AND JBERNHARD; NIELSEN, F KIEL,GE! ll ASSIGNORS TO SIGN l GE 1 w a .GESELLSCHQAFT i w mar nnsonnllrmrnnnarrower, or KIEL,

s roe, a PING- naronr srauc'ru'nns or vrnrmrron ranarcs;

Application filled October 22,1923. Serial Ito. 670,017.

To all whom itrrmg concern."

Be it known that we, HEINRICH I-IEoHT, IIUoo LICHTE, and BERNHARDNIELSEN, citizens of the German Republic, and residing t at Kiel,Germany, Province of Schleswig- Holstein, State of Prussia, haveinvented certain new and useful Improvements in Means for DampingVibratory Structures of Vibration Apparatus, of which the folno lowingis a specification.

It has been proposed to damp the motions of vibratory structures ofacoustic apparatus by causin the size "of chambers filledwith fluid anadjacent to said structures to be altered by the vibratory motions ofthese structures and allowing the fluid in the chambers to flow throughnarrow open ings in their walls. The consumption of energ required forthe damping effect is 0 cause by the passage of the fluid medium throughthe sald openings.

It has also been proposed to make these chambers very low or flat inorder to increase the damping effect.

In practical apparatus it has been found that to obtain a good dampingeflect these chambers have to be so very flat or shallow that theirconstruction is very diflicult.

In accordance with the invention these 30, chambers, instead of beingmade so extremelp shallow, are tuned to the frequency of vibratorystructures to be damped. The degree and nature of the eflect thusaccomcplished is the same; The tuning results in the medium flowingthrou h the narrow openings as violently as i very shallow chambers wereemployed.

The invention is' illustrated in the drawinfiq in which 4o ig. .1 is across section of a sound receiver fitted with a microphone and a tuneddamping-chamber,

i Fig. 2iis a mction of an electromagnetic sound apparatus (telephonereceiver) with a tuned damping chamber which may be d both for sendingand'receiving, and

Fig. 3 is a graph s owing the frequencies of resonance of an apparatusaccording to the invention. l I

The apparatus of Hi 1 is provided with a diaphragm sound ra iator towhich is attached a microphone comprising a casing 2, an electrode 3connected thereto, a; freely vibrating electrode 5 connected through theelastic member'or diaphragm4 to the casing 2. Disposed between theelectrodes in a known manner is a filling of carbon 6 which ispreventedfrom falling out by a soft packing ring 7. The damping chamber is\formed by the space in the casing 2 closed by the diaphragm 4. Thereare small openings 8 in the diaphragm 4. These openings 'andthe dampingchamber itself are of such size as to result in the damping chamberbeing tuned to the frequency of the vibratory structure '(microphone) sothat the chamber acts as a resonator and when the structure is excitedat the frequency of resonance a correspondingly strong damping efl'ectis roduced by the volume of air that passes t rough the small openings8.

In Fig. 2,.the vibratory structure itself composed 'of a diaphragm soundradiator) 9 with an armature 10. armature is a permanent magnet 11 fixedto the back-12 of the casing which envelops pposite the I the apparatus.The coils 13 receive or deliver alternating current. The subject of thisinvention consists more particularly in the narrow space 14 located atone side by the inner surface of the diaphragm, bounded at the otherside by the rigid. wall 15, and

containing air. The fluid passage in which thedamping action takes placeis the circular air gap lfi'between the armature 10 and the inner edgeof the wall or plate 15 which has the shape of a'disk with a centralhole. The dampin chamber 14 is tuned to the frequency 0 the diaphragm 9'with its armature 10.

In telephones intended for the reproduction of articulate speech the twodifferent vibratory structures or units consisting of the diaphragm andthe damping chamber respectively are preferably both tuned to afrequency of 1500 cycles and coupled together in such a manner that theresulting frequencies of resonance after coupling lie between 1000 and1500 cycles on the one hand and between 1500 and 2000 cycles on theother hand. This is represented by the graph in Fig. 3. In this graphthe abscissae denote frequencies and the ordinates the amplitudes orloudness of the apparatus shown in Fig; 2. .The dotted curve whose crestlies at 1500 represents the resonance curve of each vibratory structureor unit but instead is a chamber that any. case in constructing theapparatus.

by itself, while the solid curve is the resonance curve of the apparatuswith its vibratOIX structures cou led together. characteristic eature ofthe apparatus of Fig. 1 is' the arrangement of the damping chamberitself. The chamber employed as such is not a separate additional spaceprovided especially for dampingi purposes, evelops in This type initself is of technical importance because it leads to a simple and cheapinstrument. Of course, the chamber has to be tuned to accord with theinvention.

The damping openings ma be arranged at an parts of the walls'othe'dampmg cham n They form in their entirety the opening of theresonator which the dam ing chamber constitutes. By altering theirnumber and size this resonator can be tuned. Obviously they are bestarranged at ornear the-parts of the vibratory structure (Fig.

1 there are three vibratory units or' b0 i es to deal with, the onebeing formed by damping chamber itself,-'the second by the masses andelastic members of the microphone or elec'tro-ma net, and the third bythe diaphragm. If t e three units or bodies are all coupled togetherextremely closely the dampin' action of the damping-chamber is distriuted approximately un formly amnn the three units or bodies, particular--ly 1ft ey are all tuned to the samenatural rate of vibration. The scopeof the invention is not limited to sound'apparatus as used for examplein telephony, wire or wireless telegraphy, and sound transmission throuh air and under water etc, but includes al kinds of vibra-' tors for allmanner of technical uses. It

, can therefore also produce excellent results I in. vibratory apparatusfor balancing phases in alternatin current supply systems, apparatus inw ich vibratory structures are used for testing materials and in similarmachines.

We claim:- 1.-In acoustic apparatus,- a vibratory structure, and achamber containing fluid.- which' latter is adapted to be acted upon bysaidvibratory structure and having an ope in its wall through which'thefluid. may pass vrhen the vibratory structure is excited, said chamberbeing tuned to the frequency of the vibratory structure and being ofsuchsize and shape as to effect the desired damping of said vibratorystructure.

2. In acoustic apparatus, a vibratory structure, and a chambercontaining fluid abutting thereon and having an o ening in its wallthrough which the flui may pass when the vibratory structure is excited,said chamber being tuned to the frequency of'the vibratory structure andbeing of such size and sha e as to efiect the desired damping of saivibratory structure.

3. In acoustic apparatus, a vibratory diaphragm, and a chambercontaining fluid abutting thereon and having an opening in its wallthrough which the fluid may ass when the vibratory diaphragm is excited,said chamber bein tuned to the frequency of the vibratory iaphragm andbein of such size and shape as to eifect the desired damping of saidvibratory diaphragm.

4. In acoustic apparatus a casing having an aperture, a vibratorydiaphragm closing said aperture, and a chamber containing fluid abuttingon said vibratory diaphragm and having an opening in its wall throughwhich the fluid may pass when the vibratory diaphragm is excited, saidchamber being tuned tothe frequency of the vibratory diaphragm and beingof such size and shape as to effect the desired damping ofsaid'vibratory diaphragm.

5. In acoustic apparatus, a casing having an aperture, a vibratordiaphragm closin said aperture, a rigid p ate mounted in sai casing insuch relation to said vibratory diaphra as to form a chambertherebetween a apted to contain fluid said ri 'd plate having anaperture throu hwhich t e fluid may pass when the vi ratory diaphra m isexcited, and said chamber being tune to the frequency of the vibratorydiaphragm and being of such size and shape as to eflect the desireddamping of said vibratory diaphragm.

6. In acoustic apparatus, a vibratory structure having points executingdiflerent amplitudes of movement, and a chamber containing fluidabutting thereon and havingan opening in its wall through which thefluid may pass when the vibratory structure is excited, said openingbeing located adjacent a point of the vibratory structure havingrelatively reat amplitude of movement, and said cham r being t ed to thefrequency of the vibratory struc ure and being of such size and shape asto effect the desired damping of said vibratory structure.

7. In a vibration apparatus; an electromagnet; a primary vibratory unitconsisting of a diaphragm with an armature attached thereto located inthe held of the I magnet; a rigidplatewith'an opening in it 5 ed inaspace between the rigid plate and emoea Vibratory unit consistin offluid located in a space between the rig1 plate and the die.-

' phra-gm and in a gap between the armature and. the edge of the saidopening, the two vibratory units being each tuned to a frequency 1500.

8. In a vibration apparatus; an eleetro-' magnet; a primary vibratoryunit consist ing of, a diaphragm with .an armature attached theretolocated in the field of the magnet; a rigid plate with an opening in itadjacentthesaid armature; and a secondary vibratory unit consisting offluid .locattit the diaphragm and in a ap between the armature and theedge of t e said opening, the two vibratory units being each tuned to afrequency 1500 and coupled so that two frequencies of resonance areobtained the one lying between 1000 and 1500, and the other between'1500and2000. h

In testimony whereof we afiix our signatures in presence of twowitnesses.

' HEINRICH HECHT.

HUGO LICHTE. v BERNRD NIELSEN. Witnesses:

1E Lifi'rr, Omo Donn.

